The present invention relates to keyboard entry systems and in particular to an improved keyboard entry system which provides increased speed of data entry.
A wide variety of keyboard entry systems have been proposed in the past. Conventional QWERTY typewriter keyboards allow single finger activation of individual keys for single letter entry. Typically, keys are sequentially activated and words are entered letter by letter.
A variant of this conventional keyboard system is one which provides a control key which can be used to indicate that subsequently entered keys are to be treated in special way. For example, sequential depression of a control key and then a number of letter keys may be used to indicate that the letter keys entered subsequently to the control key are to be interpreted as a code indicative of a stored word or phrase.
Other prior art keyboard entry systems have utilized specialized keyboards which react to the simultaneous depression of several keys differently than to the sequential activation of keys. See, for example, Endfield U.S. Pat. No. 4,360,892, Prame U.S. Pat. Nos. 4,344,069 and 4,381,502 and James U.S. Pat. No. 3,381,276. For example, the Prame patents disclose a keyboard entry system in which a twelve-key pad is used. Activation of a single key results in entry of a number, whereas simultaneous activation of multiple keys results in entry of a letter.
Yet another prior art approach is that described in Binenbaum U.S. Pat. No. 3,597,538 and Budworth U.S. Pat. No. 3,892,915. Both of these systems relate to devices for use with data generated by a stenographic keyboard.
Ayres U.S. Pat. No. 3,225,883 discloses an entry system in which multiple keys are simultaneously depressed in order to enter multiple characters constituting a syllable or word. In the Ayres system, certain letters are entered by simultaneous depression of adjacent keys by a single finger of the user.
Bequaert U.S. Pat. No. 4,042,777 discloses a variant on the specialized keyboard approach. The Bequaret patent disclses a one hand keyboard which relies on simultaneous depression of one or more keys to indicate individual letters. In addition, Bequaert teaches that stored words may be retrieved by means of coded chords which do not correspond to any individual letter. Thus, when a coded chord is entered, the system disclosed by Bequaert retrieves the stored word associated with the specific chord and enters the stored word rather than the chord itself. The Bequaret system requires the simultaneous depression of two or four keys in order to entry a number of separate letters. Thus, each chorded entry must be checked to determine whether it is a letter chord indicative of a discrete letter or a coded chord indicative of a stored word. In certain applications, this need to check each chorded entry can slow the operation of the entry system to an undesirable degree. Furthermore, the Bequaert system requires an operator to learn a new entry format which differs fundamentally from that of the standard QWERTY keyboard in common use.